[1] Natl Hosp Org Minami, Dept Neurol, Okayama Med Ctr, Hayashima, Okayama 7010304, Japan
[2] Okayama Univ, Dept Neuropsychiat, Grad Sch Med Dent & Pharmaceut Sci, Shikata, Okayama, Japan
[3] Zikei Inst, Dept Lab & Med, Urayasuhon, Okayama, Japan
[4] Tohoku Univ, Grad Sch Med, Dept Pr Res, Div CJD Sci & Technol,Ctr Translat & Adv Anim Res, Seiryou, Sendai, Japan